Additive manufacturing of three-dimensional articles

ABSTRACT

A method is provided for forming a three-dimensional article through successively depositing individual layers of powder material that are fused together so as to form the article, the method comprising the steps of: providing at least one electron beam source emitting an electron beam for at least one of heating or fusing the powder material, where the electron beam source comprises a cathode, an anode, and a Wehnelt cup between the cathode and anode; providing a guard ring between the Wehnelt cup and the anode and in close proximity to the Wehnelt cup, where the guard ring is having an aperture which is larger than an aperture of the Wehnelt cup; protecting the cathode and/or the Wehnelt cup against vacuum arc discharge energy currents when forming the three-dimensional article by providing the guard ring with a higher negative potential than the Wehnelt cup and cathode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. Provisionalpatent application Ser. No. 62/344,051, filed Jun. 1, 2016, the contentsof which as are hereby incorporated by reference in their entirety.

BACKGROUND Related Field

The present invention relates to a method and apparatus for additivemanufacturing of a three dimensional article by successively fusingindividual layers of powder material.

Description of Related Art

Freeform fabrication or additive manufacturing is a method for formingthree-dimensional articles through successive fusion of chosen parts ofpowder layers applied to a worktable.

An additive manufacturing apparatus may comprise a work table on whichthe three-dimensional article is to be formed, a powder dispenser orpowder distributor, arranged to lay down a thin layer of powder on thework table for the formation of a powder bed, a high energy beam fordelivering energy to the powder whereby fusion of the powder takesplace, elements for control of the energy given off by the energy beamover the powder bed for the formation of a cross section of thethree-dimensional article through fusion of parts of the powder bed, anda controlling computer, in which information is stored concerningconsecutive cross sections of the three-dimensional article. Athree-dimensional article is formed through consecutive fusions ofconsecutively formed cross sections of powder layers, successively laiddown by the powder dispenser.

In additive manufacturing a short manufacturing time and high quality ofthe finalized product is of outmost importance. Desired materialproperties of the final product may depend on the ability to control thefusion process.

EBM (Electron Beam Melting) is one type of additive manufacturing wherean electron emitting cathode in an electron acceleration column is thesource for electron beam generation which in turn is acting as an energybeam for melting the power material. One problem is that the cathode, aswell as control electronics connected to the Wehnelt cup is verysensitive to high discharge currents which may occur in an EBM machine.The discharge current is a result of vacuum arc discharges that istriggered by contamination particles that bridges the electricacceleration field between the cathode and an anode. The contaminationparticles may be material evaporated from the fusion process and/orcontamination particles present in the vacuum chamber for other reasons.The discharge currents may destroy the cathode element and/or theWehnelt cup electronics which in turn stops the additive manufacturingprocess.

BRIEF SUMMARY

An object of the invention is to provide a method and apparatus whichprohibits that discharge currents will destroy the cathode elementand/or the Wehnelt cup electronics in an EBM additive manufacturingmachine. This object is achieved by the features in the claims providedherein.

In a first aspect of the invention it is provided a method for forming athree-dimensional article through successively depositing individuallayers of powder material that are fused together so as to form thearticle, the method comprising the steps of: providing at least oneelectron beam source emitting an electron beam for at least one ofheating or fusing the powder material, where the electron beam sourcecomprises a cathode, an anode, and a Wehnelt cup between the cathode andanode; providing a guard ring between the Wehnelt cup and the anode andin close proximity to the Wehnelt cup, where the guard ring is having anaperture which is larger than an aperture of the Wehnelt cup; andprotecting the cathode and/or the Wehnelt cup against vacuum arcdischarge energy currents when forming the three-dimensional article byproviding the guard ring with a higher negative potential than theWehnelt cup and cathode.

An exemplary and non-limiting advantage of the present invention is thatthe cathode and electronics connected to the cathode and/or Wehnelt cupis protected from vacuum arc discharge currents which may greatlyimprove the reliability of the additive manufacturing process.

In various example embodiments of the present invention the the guardring potential is fixed with reference to cathode potential. Anexemplary advantage of this embodiment is that it is simple andinexpensive to implement.

In various example embodiments of the present invention the guard ringpotential is synchronized with the grid cup potential so that the guardring potential is always 200-400V more negative than the grid cuppotential. An exemplary advantage of this embodiment is that anyinfluence of the guard ring potential is equal for all electron beamcurrents.

In various example embodiments of the present invention the guard ringis connected to an electric circuit dedicated to maintain the fixedguard ring potential during the vacuum arc discharge. An exemplaryadvantage of this embodiment is that it prevents the vacuum arcdischarge to switch from the guard ring to the cathode and/or theWhenelt cup after a certain time period during the vacuum arc discharge.The electric circuit may in its simplest form be a capacitor with asufficiently large capacitance.

In various example embodiments of the present invention the methodfurther comprising the step of aligning a center of an aperture in theWehnelt cup with a center of an aperture in the guard ring. An exemplaryadvantage of this embodiment is that the guard ring will affect theelectron beam equally in all directions.

In another aspect of the present invention it is provided a programelement configured and arranged when executed on a computer to implementa method for forming a three-dimensional article through successivelydepositing individual layers of powder material that are fused togetherso as to form the article, the method comprising the steps of: providingat least one electron beam source emitting an electron beam for at leastone of heating or fusing the powder material, where the electron beamsource comprises a cathode, an anode, and a Wehnelt cup between thecathode and anode; providing a guard ring between the Wehnelt cup andthe anode and in close proximity to the Wehnelt cup, where the guardring is having an aperture which is larger than an aperture of theWehnelt cup; wherein the guard ring is provided with a higher negativepotential than the Wehnelt cup and the cathode for protecting thecathode and/or the Wehnelt cup against vacuum arc discharge energycurrents when forming the three-dimensional article.

In another aspect of the present invention it is provided a computerprogram product comprising at least one non-transitory computer-readablestorage medium having computer-readable program code portions embodiedtherein, the computer-readable program code portions comprising at leastone executable portion configured for: providing at least one electronbeam source emitting an electron beam for at least one of heating orfusing the powder material, wherein the electron beam source comprises acathode, an anode, and a Wehnelt cup positioned between the cathode andanode; providing a guard ring between the Wehnelt cup and the anode andin close proximity to the Wehnelt cup, wherein the guard ring has anaperture larger than an aperture of the Wehnelt cup; and protecting thecathode and/or the Wehnelt cup against vacuum arc discharge energycurrents when forming the three-dimensional article by providing theguard ring with a higher negative potential than a negative potential ofthe Wehnelt cup and the cathode.

In still another aspect of the present invention it is provided anadditive manufacturing apparatus for forming a three-dimensional articlethrough successive fusion of parts of at least one layer of powderprovided on a work table, which parts corresponds to successive crosssections of the three dimensional article, the apparatus comprises atleast one electron beam source emitting an electron beam for at leastone of heating or fusing the powder material, where the electron beamsource comprises a cathode, an anode, and a Wehnelt cup between thecathode and anode; a guard ring is provided between the Wehnelt cup andthe anode and in close proximity to the Wehnelt cup, where the guardring is having an aperture which is larger than an aperture of theWehnelt cup, wherein the guard ring is provided with a higher negativepotential than the Wehnelt cup for protecting the cathode and/or theWehnelt cup against vacuum arc discharge energy currents when formingthe three-dimensional article.

All examples and exemplary embodiments described herein are non-limitingin nature and thus should not be construed as limiting the scope of theinvention described herein. Still further, the advantages describedherein, even where identified with respect to a particular exemplaryembodiment, should not be necessarily construed in such a limitingfashion.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 depicts, in a schematic cross sectional side view, an exampleembodiment of an electron beam source according to the presentinvention;

FIG. 2 depicts, in a schematic view, an example embodiment of anapparatus for producing a three dimensional product which may have anelectron beam source according to FIG. 1;

FIG. 3 depicts a schematic flow chart of an example embodiment of themethod according to the present invention.

FIG. 4 is a block diagram of an exemplary system 1020 according tovarious embodiments;

FIG. 5A is a schematic block diagram of a server 1200 according tovarious embodiments; and

FIG. 5B is a schematic block diagram of an exemplary mobile device 1300according to various embodiments.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

Various embodiments of the present invention will now be described morefully hereinafter with reference to the accompanying drawings, in whichsome, but not all embodiments of the invention are shown. Indeed,embodiments of the invention may be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein.Rather, these embodiments are provided so that this disclosure willsatisfy applicable legal requirements. Unless otherwise defined, alltechnical and scientific terms used herein have the same meaning ascommonly known and understood by one of ordinary skill in the art towhich the invention relates. The term “or” is used herein in both thealternative and conjunctive sense, unless otherwise indicated. Likenumbers refer to like elements throughout.

Still further, to facilitate the understanding of this invention, anumber of terms are defined below. Terms defined herein have meanings ascommonly understood by a person of ordinary skill in the areas relevantto the present invention. Terms such as “a”, “an” and “the” are notintended to refer to only a singular entity, but include the generalclass of which a specific example may be used for illustration. Theterminology herein is used to describe specific embodiments of theinvention, but their usage does not delimit the invention, except asoutlined in the claims.

The term “three-dimensional structures” and the like as used hereinrefer generally to intended or actually fabricated three-dimensionalconfigurations (e.g., of structural material or materials) that areintended to be used for a particular purpose. Such structures, etc. may,for example, be designed with the aid of a three-dimensional CAD system.

The term “electron beam” as used herein in various embodiments refers toany charged particle beam. The sources of charged particle beam caninclude an electron gun, a linear acceleration and so on.

The terms “Wehnelt cup” and “grid cup” have the same meaning and areused interchangeably in this document.

FIG. 2 depicts an embodiment of a freeform fabrication or additivemanufacturing apparatus 21 in which the inventive method according tothe present invention may be implemented.

The apparatus 21 comprising an electron beam gun 6; deflection coils 7;two powder hoppers 4, 14; a build platform 2; a build tank 10; a powderdistributor 28; a powder bed 5; and a vacuum chamber 20.

The vacuum chamber 20 is capable of maintaining a vacuum environment viaa vacuum system, which system may comprise a turbo molecular pump, ascroll pump, an ion pump and one or more valves which are well known toa skilled person in the art and therefore need no further explanation inthis context. The vacuum system is controlled by a control unit 8.

The electron beam gun 6 is generating an electron beam which is used forpre heating of the powder, melting or fusing together powder materialprovided on the build platform 2 or post heat treatment of the alreadyfused powder material. At least a portion of the electron beam gun 6 maybe provided in the vacuum chamber 20. The control unit 8 may be used forcontrolling and managing the electron beam emitted from the electronbeam gun 6. At least one focusing coil (not shown), at least onedeflection coil 7, an optional coil for astigmatic correction (notshown) and an electron beam power supply (not shown) may be electricallyconnected to the control unit 8. In an example embodiment of theinvention the electron beam gun 6 may generate a focusable electron beamwith an accelerating voltage of about 15-60 kV and with a beam power inthe range of 3-10 kW. The pressure in the vacuum chamber may be 10′ mbaror lower when building the three-dimensional article by fusing thepowder layer by layer with the energy beam.

The powder hoppers 4, 14 comprise the powder material to be provided onthe build platform 2 in the build tank 10. The powder material may forinstance be pure metals or metal alloys such as titanium, titaniumalloys, aluminum, aluminum alloys, stainless steel, Co—Cr alloys, nickelbased super alloys, etc.

The powder distributor 28 is arranged to lay down a thin layer of thepowder material on the build platform 2. During a work cycle the buildplatform 2 will be lowered successively in relation to a fixed point inthe vacuum chamber. In order to make this movement possible, the buildplatform 2 is in one embodiment of the invention arranged movably invertical direction, i.e., in the direction indicated by arrow P. Thismeans that the build platform 2 starts in an initial position, in whicha first powder material layer of necessary thickness has been laid down.Means for lowering the build platform 2 may for instance be through aservo motor equipped with a gear, adjusting screws, etc. The servo motormay be connected to the control unit 8.

An electron beam may be directed over the build platform 2 causing thefirst powder layer to fuse in selected locations to form a first crosssection of the three-dimensional article 3. The beam is directed overthe build platform 2 from instructions given by the control unit 8. Inthe control unit 8 instructions for how to control the electron beam foreach layer of the three-dimensional article is stored. The first layerof the three dimensional article 3 may be built on the build platform 2,which may be removable, in the powder bed 5 or on an optional startplate 16. The start plate 16 may be arranged directly on the buildplatform 2 or on top of a powder bed 5 which is provided on the buildplatform 2.

After a first layer is finished, i.e., the fusion of powder material formaking a first layer of the three-dimensional article, a second powderlayer is provided on the build platform 2. The thickness of the secondlayer may be determined by the distance the build platform is lowered inrelation to the position where the first layer was built. The secondpowder layer is in various embodiments distributed according to the samemanner as the previous layer. However, there might be alternativemethods in the same additive manufacturing machine for distributingpowder onto the work table. For instance, a first layer may be providedvia a first powder distributor 28, a second layer may be provided byanother powder distributor. The design of the powder distributor isautomatically changed according to instructions from the control unit 8.A powder distributor 28 in the form of a single rake system, i.e., whereone rake is catching powder fallen down from both a left powder hopper 4and a right powder hopper 14, the rake as such can change design.

After having distributed the second powder layer on the build platform,the energy beam is directed over the work table causing the secondpowder layer to fuse in selected locations to form a second crosssection of the three-dimensional article. Fused portions in the secondlayer may be bonded to fused portions of the first layer. The fusedportions in the first and second layer may be melted together by meltingnot only the powder in the uppermost layer but also remelting at least afraction of a thickness of a layer directly below the uppermost layer.

Sometimes it may be necessary to consider the charge distribution thatis created in the powder as the electrons hit the powder bed 5. Thecharge distribution density depends on the following parameters: beamcurrent, electron velocity (which is given by the accelerating voltage),beam scanning velocity, powder material and electrical conductivity ofthe powder, i.e., mainly the electrical conductivity between the powdergrains. The latter is in turn a function of several parameters, such asthe non-limiting examples of temperature, degree of sintering and powdergrain size/size distribution.

Thus, for a given powder, i.e., a powder of a certain material with acertain grain size distribution, and a given accelerating voltage, it ispossible, by varying the beam current (and thus the beam power) and thebeam scanning velocity, to affect the charge distribution.

By varying these parameters in a controlled way, the electricalconductivity of the powder can gradually be increased by increasing thetemperature of the powder. A powder that has a high temperature obtainsa considerably higher conductivity which results in a lower density ofthe charge distribution since the charges quickly can diffuse over alarge region. This effect is enhanced if the powder is allowed to beslightly sintered during a pre-heating process. When the conductivityhas become sufficiently high, the powder can be fused together, i.e.,melted or fully sintered, with predetermined values of the beam currentand beam scanning velocity.

FIG. 1 depicts, in a schematic cross sectional side view, an exampleembodiment of an electron beam source 100 according to the presentinvention. The electron beam source 100 comprises a cathode 101, a gridcup or Wehnelt cup 102, a guard ring 103 and an anode 104. Electrons 106emitted at the cathode 101 being on negative potential are acceleratedtowards the anode 104 and finally a target surface. The grid cup 102 isset at a predetermined distance from the cathode 101. The cathode 101may be provided with a separate power supply which may be used to heatthe cathode, where upon the cathode 101 releases electrons by thermionicemission.

An acceleration voltage 160 is provided between the cathode 101 and theanode 104. The acceleration voltage 160 causes the emitted electronsfrom the cathode 101 to accelerate towards the anode 104 thusestablishing an electron beam 106. The electron beam 106 may impinge ona substrate surface, which may be a powder layer in an additivemanufacturing process. In order to guide and focus the electron beamthere may further be arranged at least one focusing coil and at leastone deflection coil.

In the electron beam source 100 the grid cup 102 is provided between thecathode 101 and the anode 104. The grid cup 102 may be arranged as aplate having an aperture 112. The aperture 112 may be aligned with thecathode 101. The size of the aperture 112 in the grid cup 102 maycorrespond to a cross section of the electron beam 106 at the positionof the grid cup 102.

A grid cup voltage 180 may be provided between the grid cup 102 and thecathode 101 and may be adjusted between a negative blocking voltage anda full power voltage and thereby adjusting an electron beam currentbetween 0—maximum electron beam current. In FIG. 1 the cathode 101 maybe provided with a negative potential of −20 kV to −100 kV.

The grid cup voltage 180 may be varied between the negative blockingvoltage and the full power voltage. A second control unit 150 may becontrolling the grid cup voltage 180 in order to adjust the electronbeam current to a desired value as well as the acceleration voltage 160and a guard ring voltage 170. The second control unit 150 may be aphysically separate control unit in connection with the control unit 8or fully integrated in the control unit 8.

The anode may be set to ground potential. The target surface 118 may beset to ground potential or a positive potential. The electron beamsource 100 may also comprise means for detecting the actual electronbeam current. An example means for detecting the electron beam currenton the target surface may be to detect the actual loading of the highvoltage source providing the acceleration voltage 160. If the cathode isprovided with a fixed negative voltage of −60 kV the negative blockingvoltage may be around −61 kV, i.e., the Wehnelt cup 102 itself is set at−61 kV, for blocking the electrons by the grid cup 102. If starting todecrease the negative blocking voltage, some of the electrons emittedfrom the cathode will be allowed to pass through the grid cup 102. Byvarying the grid cup voltage in this example embodiment between −61 kVto ˜−60 kV, when the cathode is provided with a fixed negative potentialof −60kV, the electron beam current may vary from OmA—maximum electronbeam current which may be 25 mA for a predetermined size and shape ofthe cathode 101 and a predetermined size and shape of the aperture inthe grid cup 102. Other acceleration voltages and/or other size, shapeand emissivity of the cathode 101 and/or other size and shape of theaperture in the grid cup 102 may affect the maximum electron beamcurrent to be higher or lower than the exemplified 25 mA.

The guard ring 103 may be arranged between the Wehnelt cup 102 and theanode 104 and in close proximity to the Wehnelt cup 102. The guard ring103 may be provided with more negative potential than the Wehnelt cup102 in order to diverge vacuum discharge arcs from the cathode 101and/or Wehnelt cup 102 towards and onto the guard ring 103. In FIG. 1 apre-discharge channel 107 may be present between the anode 104 and thecathode 101 if no guard ring 103 is present. However, a diverteddischarge channel 108 between the anode 104 and the guard ring 103 maybe present if the guard ring 103 is arranged with a more negativeelectric potential than the Wehnelt cup 102. A guard ring potential 170may be fixed and connected to a bulk capacitance 105 of sufficient sizeto maintain its relative voltage to the Wehnelt cup 102 and cathode 101during any possible vacuum discharge. The guard ring potential 170 iswhat controls the electric field strength that attracts and diverges thedeveloping pre-discharge arc channel 107 from the anode 104 to thecathode 101 and/or Wehnelt cup 102 into a diverted discharge channel 108from the anode 104 to the guard ring 103.

A guard ring aperture 114 needs to be somewhat larger than the Wehneltcup aperture 112 in order not to interfere with the electric fieldcontrolling the electron emission from the cathode 101. In an exampleembodiment the aperture 114 in the guard ring 103 may be 10% larger thanthe aperture 112 of the Wehnelt cup 102. In an example embodiment theWehnelt cup 102 may have an aperture 112 of 3 mm and the guard ring 103may have an aperture 114 of 3.3 mm.

If the grid cup potential is varied between −61 kV-−60 kV the guard ringpotential needs to be around −61.5 kV if set to a fixed value.Alternatively the guard ring potential 170 may by synchronized with thegrid cup potential 180 and may always being set to a potential −200-−400lower than the grid cup potential 180.

The distance between the Guard ring and the Wehnelt cup in a directiontowards the anode 104 may be a few mm.

FIG. 3 depicts a schematic flow chart of an example embodiment of themethod for forming a three-dimensional article through successivelydepositing individual layers of powder material that are fused togetherso as to form the article.

In a first step 310 at least one electron beam source is provided foremitting an electron beam for at least one of heating or fusing thepowder material, where the electron beam source comprises a cathode, ananode, and a Wehnelt cup between the cathode and anode.

In a second step 320 a guard ring is provided between the Wehnelt cupand the anode and in close proximity to the Wehnelt cup, where the guardring is having an aperture which is larger than an aperture of theWehnelt cup.

In a third step 330 the cathode and/or the Wehnelt cup is protectedagainst vacuum arc discharge energy currents when forming thethree-dimensional article by providing the guard ring with a highernegative potential than the Wehnelt cup and cathode.

In another aspect of the invention it is provided a program elementconfigured and arranged when executed on a computer to implement amethod for forming a three-dimensional article through successivelydepositing individual layers of powder material that are fused togetherso as to form the article, the method comprising the steps of: providingat least one electron beam source emitting an electron beam for heatingand/or fusing the powder material, where the electron beam sourcecomprising a cathode, an anode, and a grid cup between the cathode andanode, controlling the electron beam source in a first mode when theformation of the three dimensional article is in a first process step,controlling the electron beam source in a second mode when the formationof the three dimensional article is in a second process step, wherein anelectron beam current from the electron beam source is controlled in afeed-forward mode in the first mode and the electron beam current iscontrolled in a feed-back mode in the second mode. The program may beinstalled in a computer readable storage medium. The computer readablestorage medium may be the control unit 8, the control unit 150, oranother separate and distinct control unit. The computer readablestorage medium and the program element, which may comprisecomputer-readable program code portions embodied therein, may further becontained within a non-transitory computer program product. Furtherdetails regarding these features and configurations are provided, inturn, below.

As mentioned, various embodiments of the present invention may beimplemented in various ways, including as non-transitory computerprogram products. A computer program product may include anon-transitory computer-readable storage medium storing applications,programs, program modules, scripts, source code, program code, objectcode, byte code, compiled code, interpreted code, machine code,executable instructions, and/or the like (also referred to herein asexecutable instructions, instructions for execution, program code,and/or similar terms used herein interchangeably). Such non-transitorycomputer-readable storage media include all computer-readable media(including volatile and non-volatile media).

In one embodiment, a non-volatile computer-readable storage medium mayinclude a floppy disk, flexible disk, hard disk, solid-state storage(SSS) (e.g., a solid state drive (SSD), solid state card (SSC), solidstate module (SSM)), enterprise flash drive, magnetic tape, or any othernon-transitory magnetic medium, and/or the like. A non-volatilecomputer-readable storage medium may also include a punch card, papertape, optical mark sheet (or any other physical medium with patterns ofholes or other optically recognizable indicia), compact disc read onlymemory (CD-ROM), compact disc compact disc-rewritable (CD-RW), digitalversatile disc (DVD), Blu-ray disc (BD), any other non-transitoryoptical medium, and/or the like. Such a non-volatile computer-readablestorage medium may also include read-only memory (ROM), programmableread-only memory (PROM), erasable programmable read-only memory (EPROM),electrically erasable programmable read-only memory (EEPROM), flashmemory (e.g., Serial, NAND, NOR, and/or the like), multimedia memorycards (MMC), secure digital (SD) memory cards, SmartMedia cards,CompactFlash (CF) cards, Memory Sticks, and/or the like. Further, anon-volatile computer-readable storage medium may also includeconductive-bridging random access memory (CBRAM), phase-change randomaccess memory (PRAM), ferroelectric random-access memory (FeRAM),non-volatile random-access memory (NVRAM), magnetoresistiverandom-access memory (MRAM), resistive random-access memory (RRAM),Silicon-Oxide-Nitride-Oxide-Silicon memory (SONOS), floating junctiongate random access memory (FJG RAM), Millipede memory, racetrack memory,and/or the like.

In one embodiment, a volatile computer-readable storage medium mayinclude random access memory (RAM), dynamic random access memory (DRAM),static random access memory (SRAM), fast page mode dynamic random accessmemory (FPM DRAM), extended data-out dynamic random access memory (EDODRAM), synchronous dynamic random access memory (SDRAM), double datarate synchronous dynamic random access memory (DDR SDRAM), double datarate type two synchronous dynamic random access memory (DDR2 SDRAM),double data rate type three synchronous dynamic random access memory(DDR3 SDRAM), Rambus dynamic random access memory (RDRAM), TwinTransistor RAM (TTRAM), Thyristor RAM (T-RAM), Zero-capacitor (Z-RAM),Rambus in-line memory module (RIMM), dual in-line memory module (DIMM),single in-line memory module (SIMM), video random access memory VRAM,cache memory (including various levels), flash memory, register memory,and/or the like. It will be appreciated that where embodiments aredescribed to use a computer-readable storage medium, other types ofcomputer-readable storage media may be substituted for or used inaddition to the computer-readable storage media described above.

As should be appreciated, various embodiments of the present inventionmay also be implemented as methods, apparatus, systems, computingdevices, computing entities, and/or the like, as have been describedelsewhere herein. As such, embodiments of the present invention may takethe form of an apparatus, system, computing device, computing entity,and/or the like executing instructions stored on a computer-readablestorage medium to perform certain steps or operations. However,embodiments of the present invention may also take the form of anentirely hardware embodiment performing certain steps or operations.

Various embodiments are described below with reference to block diagramsand flowchart illustrations of apparatuses, methods, systems, andcomputer program products. It should be understood that each block ofany of the block diagrams and flowchart illustrations, respectively, maybe implemented in part by computer program instructions, e.g., aslogical steps or operations executing on a processor in a computingsystem. These computer program instructions may be loaded onto acomputer, such as a special purpose computer or other programmable dataprocessing apparatus to produce a specifically-configured machine, suchthat the instructions which execute on the computer or otherprogrammable data processing apparatus implement the functions specifiedin the flowchart block or blocks.

These computer program instructions may also be stored in acomputer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture including computer-readableinstructions for implementing the functionality specified in theflowchart block or blocks. The computer program instructions may also beloaded onto a computer or other programmable data processing apparatusto cause a series of operational steps to be performed on the computeror other programmable apparatus to produce a computer-implementedprocess such that the instructions that execute on the computer or otherprogrammable apparatus provide operations for implementing the functionsspecified in the flowchart block or blocks.

Accordingly, blocks of the block diagrams and flowchart illustrationssupport various combinations for performing the specified functions,combinations of operations for performing the specified functions andprogram instructions for performing the specified functions. It shouldalso be understood that each block of the block diagrams and flowchartillustrations, and combinations of blocks in the block diagrams andflowchart illustrations, could be implemented by special purposehardware-based computer systems that perform the specified functions oroperations, or combinations of special purpose hardware and computerinstructions.

FIG. 4 is a block diagram of an exemplary system 1020 that can be usedin conjunction with various embodiments of the present invention. In atleast the illustrated embodiment, the system 1020 may include one ormore central computing devices 1110, one or more distributed computingdevices 1120, and one or more distributed handheld or mobile devices1300, all configured in communication with a central server 1200 (orcontrol unit) via one or more networks 1130. While FIG. 4 illustratesthe various system entities as separate, standalone entities, thevarious embodiments are not limited to this particular architecture.

According to various embodiments of the present invention, the one ormore networks 1130 may be capable of supporting communication inaccordance with any one or more of a number of second-generation (2 G),2.5 G, third-generation (3 G), and/or fourth-generation (4 G) mobilecommunication protocols, or the like. More particularly, the one or morenetworks 1130 may be capable of supporting communication in accordancewith 2 G wireless communication protocols IS-136 (TDMA), GSM, and IS-95(CDMA). Also, for example, the one or more networks 1130 may be capableof supporting communication in accordance with 2.5 G wirelesscommunication protocols GPRS, Enhanced Data GSM Environment (EDGE), orthe like. In addition, for example, the one or more networks 1130 may becapable of supporting communication in accordance with 3 G wirelesscommunication protocols such as Universal Mobile Telephone System (UMTS)network employing Wideband Code Division Multiple Access (WCDMA) radioaccess technology. Some narrow-band AMPS (NAMPS), as well as TACS,network(s) may also benefit from embodiments of the present invention,as should dual or higher mode mobile stations (e.g., digital/analog orTDMA/CDMA/analog phones). As yet another example, each of the componentsof the system 1020 may be configured to communicate with one another inaccordance with techniques such as, for example, radio frequency (RF),Bluetooth™ infrared (IrDA), or any of a number of different wired orwireless networking techniques, including a wired or wireless PersonalArea Network (“PAN”), Local Area Network (“LAN”), Metropolitan AreaNetwork (“MAN”), Wide Area Network (“WAN”), or the like.

Although the device(s) 1110-1300 are illustrated in FIG. 4 ascommunicating with one another over the same network 1130, these devicesmay likewise communicate over multiple, separate networks.

According to one embodiment, in addition to receiving data from theserver 1200, the distributed devices 1110, 1120, and/or 1300 may befurther configured to collect and transmit data on their own. In variousembodiments, the devices 1110, 1120, and/or 1300 may be capable ofreceiving data via one or more input units or devices, such as a keypad,touchpad, barcode scanner, radio frequency identification (RFID) reader,interface card (e.g., modem, etc.) or receiver. The devices 1110, 1120,and/or 1300 may further be capable of storing data to one or morevolatile or non-volatile memory modules, and outputting the data via oneor more output units or devices, for example, by displaying data to theuser operating the device, or by transmitting data, for example over theone or more networks 1130.

In various embodiments, the server 1200 includes various systems forperforming one or more functions in accordance with various embodimentsof the present invention, including those more particularly shown anddescribed herein. It should be understood, however, that the server 1200might include a variety of alternative devices for performing one ormore like functions, without departing from the spirit and scope of thepresent invention. For example, at least a portion of the server 1200,in certain embodiments, may be located on the distributed device(s)1110, 1120, and/or the handheld or mobile device(s) 1300, as may bedesirable for particular applications. As will be described in furtherdetail below, in at least one embodiment, the handheld or mobiledevice(s) 1300 may contain one or more mobile applications 1330 whichmay be configured so as to provide a user interface for communicationwith the server 1200, all as will be likewise described in furtherdetail below.

FIG. 5A is a schematic diagram of the server 1200 according to variousembodiments. The server 1200 includes a processor 1230 that communicateswith other elements within the server via a system interface or bus1235. Also included in the server 1200 is a display/input device 1250for receiving and displaying data. This display/input device 1250 maybe, for example, a keyboard or pointing device that is used incombination with a monitor. The server 1200 further includes memory1220, which preferably includes both read only memory (ROM) 1226 andrandom access memory (RAM) 1222. The server's ROM 1226 is used to storea basic input/output system 1224 (BIOS), containing the basic routinesthat help to transfer information between elements within the server1200. Various ROM and RAM configurations have been previously describedherein.

In addition, the server 1200 includes at least one storage device orprogram storage 210, such as a hard disk drive, a floppy disk drive, aCD Rom drive, or optical disk drive, for storing information on variouscomputer-readable media, such as a hard disk, a removable magnetic disk,or a CD-ROM disk. As will be appreciated by one of ordinary skill in theart, each of these storage devices 1210 are connected to the system bus1235 by an appropriate interface. The storage devices 1210 and theirassociated computer-readable media provide nonvolatile storage for apersonal computer. As will be appreciated by one of ordinary skill inthe art, the computer-readable media described above could be replacedby any other type of computer-readable media known in the art. Suchmedia include, for example, magnetic cassettes, flash memory cards,digital video disks, and Bernoulli cartridges.

Although not shown, according to an embodiment, the storage device 1210and/or memory of the server 1200 may further provide the functions of adata storage device, which may store historical and/or current deliverydata and delivery conditions that may be accessed by the server. In thisregard, the storage device 1210 may comprise one or more databases. Theterm “database” refers to a structured collection of records or datathat is stored in a computer system, such as via a relational database,hierarchical database, or network database and as such, should not beconstrued in a limiting fashion.

A number of program modules (e.g., exemplary modules 1400-1700)comprising, for example, one or more computer-readable program codeportions executable by the processor 1230, may be stored by the variousstorage devices 1210 and within RAM 1222. Such program modules may alsoinclude an operating system 1280. In these and other embodiments, thevarious modules 1400, 1500, 1600, 1700 control certain aspects of theoperation of the server 1200 with the assistance of the processor 1230and operating system 1280. In still other embodiments, it should beunderstood that one or more additional and/or alternative modules mayalso be provided, without departing from the scope and nature of thepresent invention.

In various embodiments, the program modules 1400, 1500, 1600, 1700 areexecuted by the server 1200 and are configured to generate one or moregraphical user interfaces, reports, instructions, and/ornotifications/alerts, all accessible and/or transmittable to varioususers of the system 1020. In certain embodiments, the user interfaces,reports, instructions, and/or notifications/alerts may be accessible viaone or more networks 1130, which may include the Internet or otherfeasible communications network, as previously discussed.

In various embodiments, it should also be understood that one or more ofthe modules 1400, 1500, 1600, 1700 may be alternatively and/oradditionally (e.g., in duplicate) stored locally on one or more of thedevices 1110, 1120, and/or 1300 and may be executed by one or moreprocessors of the same. According to various embodiments, the modules1400, 1500, 1600, 1700 may send data to, receive data from, and utilizedata contained in one or more databases, which may be comprised of oneor more separate, linked and/or networked databases.

Also located within the server 1200 is a network interface 1260 forinterfacing and communicating with other elements of the one or morenetworks 1130. It will be appreciated by one of ordinary skill in theart that one or more of the server 1200 components may be locatedgeographically remotely from other server components. Furthermore, oneor more of the server 1060 components may be combined, and/or additionalcomponents performing functions described herein may also be included inthe server.

While the foregoing describes a single processor 1230, as one ofordinary skill in the art will recognize, the server 1200 may comprisemultiple processors operating in conjunction with one another to performthe functionality described herein. In addition to the memory 1220, theprocessor 1230 can also be connected to at least one interface or othermeans for displaying, transmitting and/or receiving data, content or thelike. In this regard, the interface(s) can include at least onecommunication interface or other means for transmitting and/or receivingdata, content or the like, as well as at least one user interface thatcan include a display and/or a user input interface, as will bedescribed in further detail below. The user input interface, in turn,can comprise any of a number of devices allowing the entity to receivedata from a user, such as a keypad, a touch display, a joystick or otherinput device.

Still further, while reference is made to the “server” 1200, as one ofordinary skill in the art will recognize, embodiments of the presentinvention are not limited to traditionally defined server architectures.Still further, the system of embodiments of the present invention is notlimited to a single server, or similar network entity or mainframecomputer system. Other similar architectures including one or morenetwork entities operating in conjunction with one another to providethe functionality described herein may likewise be used withoutdeparting from the spirit and scope of embodiments of the presentinvention. For example, a mesh network of two or more personal computers(PCs), similar electronic devices, or handheld portable devices,collaborating with one another to provide the functionality describedherein in association with the server 1200 may likewise be used withoutdeparting from the spirit and scope of embodiments of the presentinvention.

According to various embodiments, many individual steps of a process mayor may not be carried out utilizing the computer systems and/or serversdescribed herein, and the degree of computer implementation may vary, asmay be desirable and/or beneficial for one or more particularapplications.

FIG. 5B provides an illustrative schematic representative of a mobiledevice 1300 that can be used in conjunction with various embodiments ofthe present invention. Mobile devices 1300 can be operated by variousparties. As shown in FIG. 5B, a mobile device 1300 may include anantenna 1312, a transmitter 1304 (e.g., radio), a receiver 1306 (e.g.,radio), and a processing element 1308 that provides signals to andreceives signals from the transmitter 1304 and receiver 1306,respectively.

The signals provided to and received from the transmitter 1304 and thereceiver 1306, respectively, may include signaling data in accordancewith an air interface standard of applicable wireless systems tocommunicate with various entities, such as the server 1200, thedistributed devices 1110, 1120, and/or the like. In this regard, themobile device 1300 may be capable of operating with one or more airinterface standards, communication protocols, modulation types, andaccess types. More particularly, the mobile device 1300 may operate inaccordance with any of a number of wireless communication standards andprotocols. In a particular embodiment, the mobile device 1300 mayoperate in accordance with multiple wireless communication standards andprotocols, such as GPRS, UMTS, CDMA2000, 1xRTT, WCDMA, TD-SCDMA, LTE,E-UTRAN, EVDO, HSPA, HSDPA, Wi-Fi, WiMAX, UWB, IR protocols, Bluetoothprotocols, USB protocols, and/or any other wireless protocol.

Via these communication standards and protocols, the mobile device 1300may according to various embodiments communicate with various otherentities using concepts such as Unstructured Supplementary Service data(USSD), Short Message Service (SMS), Multimedia Messaging Service (MMS),Dual-Tone Multi-Frequency Signaling (DTMF), and/or Subscriber IdentityModule Dialer (SIM dialer). The mobile device 1300 can also downloadchanges, add-ons, and updates, for instance, to its firmware, software(e.g., including executable instructions, applications, programmodules), and operating system.

According to one embodiment, the mobile device 1300 may include alocation determining device and/or functionality. For example, themobile device 1300 may include a GPS module adapted to acquire, forexample, latitude, longitude, altitude, geocode, course, and/or speeddata. In one embodiment, the GPS module acquires data, sometimes knownas ephemeris data, by identifying the number of satellites in view andthe relative positions of those satellites.

The mobile device 1300 may also comprise a user interface (that caninclude a display 1316 coupled to a processing element 1308) and/or auser input interface (coupled to a processing element 1308). The userinput interface can comprise any of a number of devices allowing themobile device 1300 to receive data, such as a keypad 1318 (hard orsoft), a touch display, voice or motion interfaces, or other inputdevice. In embodiments including a keypad 1318, the keypad can include(or cause display of) the conventional numeric (0-9) and related keys(#, *), and other keys used for operating the mobile device 1300 and mayinclude a full set of alphabetic keys or set of keys that may beactivated to provide a full set of alphanumeric keys. In addition toproviding input, the user input interface can be used, for example, toactivate or deactivate certain functions, such as screen savers and/orsleep modes.

The mobile device 1300 can also include volatile storage or memory 1322and/or non-volatile storage or memory 1324, which can be embedded and/ormay be removable. For example, the non-volatile memory may be ROM, PROM,EPROM, EEPROM, flash memory, MMCs, SD memory cards, Memory Sticks,CBRAM, PRAM, FeRAM, RRAM, SONOS, racetrack memory, and/or the like. Thevolatile memory may be RAM, DRAM, SRAM, FPM DRAM, EDO DRAM, SDRAM, DDRSDRAM, DDR2 SDRAM, DDR3 SDRAM, RDRAM, RIMM, DIMM, SIMM, VRAM, cachememory, register memory, and/or the like. The volatile and non-volatilestorage or memory can store databases, database instances, databasemapping systems, data, applications, programs, program modules, scripts,source code, object code, byte code, compiled code, interpreted code,machine code, executable instructions, and/or the like to implement thefunctions of the mobile device 1300.

The mobile device 1300 may also include one or more of a camera 1326 anda mobile application 1330. The camera 1326 may be configured accordingto various embodiments as an additional and/or alternative datacollection feature, whereby one or more items may be read, stored,and/or transmitted by the mobile device 1300 via the camera. The mobileapplication 1330 may further provide a feature via which various tasksmay be performed with the mobile device 1300. Various configurations maybe provided, as may be desirable for one or more users of the mobiledevice 1300 and the system 1020 as a whole.

It will be appreciated that many variations of the above systems andmethods are possible, and that deviation from the above embodiments arepossible, but yet within the scope of the claims. Many modifications andother embodiments of the inventions set forth herein will come to mindto one skilled in the art to which these inventions pertain having thebenefit of the teachings presented in the foregoing descriptions and theassociated drawings. Therefore, it is to be understood that theinventions are not to be limited to the specific embodiments disclosedand that modifications and other embodiments are intended to be includedwithin the scope of the appended claims. Such modifications may, forexample, involve using multiple energy beam sources instead of theexemplified single electron beam source. Still further, althoughspecific terms are employed herein, they are used in a generic anddescriptive sense only and not for purposes of limitation.

1. A method for forming a three-dimensional article through successivelydepositing individual layers of powder material that are fused togetherso as to form the article, the method comprising the steps of: providingat least one electron beam source emitting an electron beam for at leastone of heating or fusing the powder material, wherein the electron beamsource comprises a cathode, an anode, and a Wehnelt cup positionedbetween the cathode and anode; providing a guard ring between theWehnelt cup and the anode and in close proximity to the Wehnelt cup,wherein the guard ring has an aperture larger than an aperture of theWehnelt cup; and protecting at least one of the cathode or the Wehneltcup against vacuum arc discharge energy currents when forming thethree-dimensional article by providing the guard ring with a highernegative potential than a negative potential of the Wehnelt cup and thecathode.
 2. The method according to claim 1, wherein the guard ringpotential is fixed with reference to cathode potential.
 3. The methodaccording to claim 1, wherein the guard ring potential is synchronizedwith the grid cup potential so that the guard ring potential is always200-400V more negative than the grid cup potential.
 4. The methodaccording to claim 1, wherein the guard ring is connected to an electriccircuit dedicated to maintain the fixed guard ring potential during thevacuum arc discharge.
 5. The method according to claim 1, furthercomprising the step of aligning a center of an aperture in the Wehneltcup with a center of an aperture in the guard ring.
 6. The methodaccording to claim 1, wherein one or more of the steps recited thereinare computer-implemented via at least one control unit or processor. 7.A computer program product comprising at least one non-transitorycomputer-readable storage medium having computer-readable program codeportions embodied therein, the computer-readable program code portionscomprising at least one executable portion configured for: providing atleast one electron beam source emitting an electron beam for at leastone of heating or fusing the powder material, wherein the electron beamsource comprises a cathode, an anode, and a Wehnelt cup positionedbetween the cathode and anode; providing a guard ring between theWehnelt cup and the anode and in close proximity to the Wehnelt cup,wherein the guard ring has an aperture larger than an aperture of theWehnelt cup; and protecting the cathode and/or the Wehnelt cup againstvacuum arc discharge energy currents when forming the three-dimensionalarticle by providing the guard ring with a higher negative potentialthan a negative potential of the Wehnelt cup and the cathode.
 8. Thecomputer program product according to claim 7, wherein the at least oneexecutable portion is configured such that the guard ring potential isfixed with reference to cathode potential.
 9. The computer programproduct according to claim 7, wherein the at least one executableportion is configured such that the the guard ring potential issynchronized with the grid cup potential so that the guard ringpotential is always 200-400V more negative than the grid cup potential.10. The computer program product according to claim 7, wherein the guardring is connected to an electric circuit dedicated to maintain the fixedguard ring potential during the vacuum arc discharge.
 11. The computerprogram product according to claim 7, wherein the at least oneexecutable portion is configured for aligning a center of an aperture inthe Wehnelt cup with a center of an aperture in the guard ring.
 12. Anadditive manufacturing apparatus for forming a three-dimensional articlethrough successive fusion of parts of at least one layer of powderprovided on a work table, which parts corresponds to successive crosssections of the three dimensional article, the apparatus comprising: atleast one electron beam source emitting an electron beam for at leastone of heating or fusing the powder material, the electron beam sourcecomprising a cathode, an anode, and a Wehnelt cup between the cathodeand anode; and a guard ring positioned between the Wehnelt cup and theanode and in close proximity to the Wehnelt cup, the guard ring havingan aperture larger than an aperture of the Wehnelt cup, wherein theguard ring is provided with a higher negative potential than the Wehneltcup for protecting at least one of the cathode or the Wehnelt cupagainst vacuum arc discharge energy currents when forming thethree-dimensional article.
 13. The apparatus according to claim 12,wherein the guard ring is connected to an electric circuit dedicated tomaintain the fixed guard ring potential during the vacuum arc discharge.14. The apparatus according to claim 12, further comprising asynchronizing unit for synchronizing the guard ring potential with thegrid cup potential so that the guard ring potential is always 200-400Vmore negative than the grid cup potential.
 15. The apparatus accordingto claim 12, wherein a center of an aperture in the Wehnelt cup isaligned with a center of an aperture in the guard ring.